Three members of the Saudi royal family have been arrested, according to reports in US media, in what is interpreted to be an attempt to strengthen the grip on power of Crown Prince Mohammed bin Salman, also known as MBS.

The Wall Street Journal reports that two of Saudi Araba's most prominent figures were held for an alleged coup attempt to oust King Salman and the son designated to succeed him, the crown prince.

Quoting unidentified sources, the Journal said guards from the royal court detained one of the king's brothers, Prince Ahmed bin Abdulaziz al Saud, and one of his nephews, Prince Mohammed bin Nayef. Both men were arrested at their homes and charged with treason, it said.

According to the Times, a possible reason for the arrests could be a move by MBS -- already the country's effective leader -- to counter potential challengers to his succession after King Salman, who is 84, dies or leaves the throne.

Mohammed bin Nayef, a once powerful figure as head of Saudi counterterrorism efforts, had been crown prince until 2017, when King Salman took away the title and put his son first in line for the throne of the longtime US ally.

The crown prince, who is in charge of day-to-day governance in the kingdom, has been praised in the West for implementing social reforms, but he also has drawn intense criticism for a tough crackdown on Saudis perceived as critics of his policies.

In 2017 dozens of royal figures as well as ministers and businessmen were arrested in what was seen as a purge to boost the power of the crown prince.

MBS also came under scrutiny after the 2018 killing of Saudi dissident and Washington Post columnist Jamal Khashoggi inside the Saudi consulate in Istanbul. Critics accused him of being linked to the slaying, but he denied it. A Saudi court sentenced five people to death for the killing, but did not hold any high-ranking officials responsible.

Saudi Arabia has also been harshly criticised for its war in Yemen, which has led to the world's worst humanitarian disaster.